A question of justice

Suppose a serial killer like Jeffrey Dahmer enjoys a lifestyle torturing, killing and cannibalizing people for fun. He eventually gets caught and goes to prison. In prison he becomes a born-again Christian and all this sins are absolved from him. He then gets killed and goes to heaven since the mere act of conversion into Christianity cleanses him of all previous wrong doings. Some of this victims however were not Christian when they were murdered and so they go to hell when they die. So not only are the murder victims tortured and murdered in this world, they get sent to hell to be tortured even worse, but now it is forever, while their murderer enjoys everlasting peace in heaven